1. Technical Field
The invention concerns a coupling for two electromagnetic hollow conductors (waveguides) with different cross-sectional shapes, containing steps arranged sequentially in the axial direction, having an essentially rectangular cross section and rounded corners as well as different clearances (open areas or clear width), in which a low-reflective transmission of the wave modes (modes or modes of propagation) intended to conduct signals takes place.
2. Description of the Prior Art
A coupling for two electromagnetic hollow conductors (waveguides) with different cross-sectional shapes is also called a "transition" and has the task of transferring the signal conducting wave mode (mode) of a waveguide without reflections into the mode of the other waveguide that is intended to conduct signals. The coupling becomes necessary when the two waveguides to be joined have different cross sections and a direct connection would cause too many reflections. The two waveguides can basically have any cross-sectional shape. For example, they can be elliptical, rectangular, square or round.
It is known in conventional technology to join waveguides of different cross-sectional shapes with a coupling which continuously changes from one cross-sectional shape to the other along the length (DE-AS 14 91 901). Such couplings have good electrical properties. However, they are very costly to produce. In addition, they are very long because their length must be a multiple of the waveguide's length.
A stepped coupling in accordance with the EP 0 145 292 A2 mentioned earlier is shorter. The use of this known coupling with step-like changes in its cross-sectional geometry is exclusively limited to frequency ranges in which only the respective basic wave is able to propagate in the two waveguides as well as in the coupling itself. In each case, the cross sections of the individual coupling steps are chosen so that other types of waves are unable to propagate therein. This known coupling is therefore limited to single-mode operation. It is exclusively used to transmit the basic modes of the respective waveguides being joined. It is furthermore assumed that the individual steps widen or narrow uniformly from one end of the coupling to the other, so that the limiting frequency of the basic mode changes monotonically within the coupling. Finally, the coupling is only designed to link a rectangular waveguide to an elliptical one.